[SPARK-10181][SQL] Do kerberos login for credentials during hive client initialization

On driver process start up, UserGroupInformation.loginUserFromKeytab is called with the principal and keytab passed in, and therefore static var UserGroupInfomation,loginUser is set to that principal with kerberos credentials saved in its private credential set, and all threads within the driver process are supposed to see and use this login credentials to authenticate with Hive and Hadoop. However, because of IsolatedClientLoader, UserGroupInformation class is not shared for hive metastore clients, and instead it is loaded separately and of course not able to see the prepared kerberos login credentials in the main thread.

The first proposed fix would cause other classloader conflict errors, and is not an appropriate solution. This new change does kerberos login during hive client initialization, which will make credentials ready for the particular hive client instance.

 yhuai Please take a look and let me know. If you are not the right person to talk to, could you point me to someone responsible for this?

Author: Yu Gao <ygao@us.ibm.com>
Author: gaoyu <gaoyu@gaoyu-macbookpro.roam.corp.google.com>
Author: Yu Gao <crystalgaoyu@gmail.com>

Closes #9272 from yolandagao/master.